The season's first ice formation was recorded Friday on the Han River, which bisects Seoul, as the mercury fell to a morning low of 10 C below zero in many areas, the weather agency said.The Korea Meteorological Administration (KMA) observed the first ice formation on the river, 42 days earlier than last winter's first ice, which occurred Jan. 26 this year, and 29 days earlier than the average.It also marked the earliest ice formation on the river since Dec. 12, 1946, the administration said.As of 7:40 a.m., temperatures hit a low of minus 7.5 C in Seoul. The city saw daily lows dip to 10 C below zero and highs remain at subzero levels Monday through Thursday.The weather agency says that it declares that ice has formed on the Han when there is ice on a 100 meter area from north to south between the second and fourth piers of the Hangang Bridge, near Noryangjin in the southern part of the capital. The thickness of the ice is irrelevant to the declaration, as long as it covers the whole area.Since observations of ice formation on the river started in 1906, the earliest ice formation was recorded on Dec. 4, 1934, and the latest one was on Feb. 13, 1964.There have been seven times when no ice formation was observed, most recently in 2006. (Yonhap)